Fat-Burn Feedback

An at-home breath test can tell dieters if they are burning fat. The handheld device—featuring a straw that users blow into for six seconds—measures levels of acetone, a chemical released in the body when it breaks down fat. In a two-week study of 17 volunteers, those who lost weight had daily acetone levels that rose as their body fat decreased (or fell as their fat loss plateaued). It could take weeks for diet success or failure to register on a scale; in contrast, this device gives fast and precise feedback that can help dieters adjust their next meal or workout, says Tsuguyoshi Toyooka, a researcher at NTT Docomo, the Japanese company that developed the device (which pairs with a smartphone). If other ongoing studies of the analyzer are also favorable, it could be available within a couple of years, he says.